Compute beam charge asymmetry using helicity gated scalers.

Add parameters to hold helicity scaler results:
  g%s_hscaler_plus[%d]
  g%s_hscaler_minus[%d]
  g%s_hscaler_sum[%d]
  g%s_hscaler_asy[%d]
  g%s_hscaler_asyerr[%d]
  g%s_hscaler_time (Time with defined helicity)
  g%s_hscaler_time_asy
  g%s_hscaler_triggers	(All triggers including where helicity not decoded)
  g%s_hscaler_triggers_plus
  g%s_hscaler_triggers_minus  (plus+minus is slightly less than triggers)
  g%s_hscaler_trigger_asy

%s is name assigned to THcHelicityScaler object
%d is scaler channel #.  0-31